What is the recommended dosing for furosemide (Lasix)?

Furosemide Recommended Dosing

For most clinical situations, start with furosemide 20-40 mg orally or intravenously as a single dose, with the specific starting dose and route determined by the underlying condition, severity of fluid overload, and prior diuretic exposure. 1, 2, 3

Initial Dosing by Clinical Condition

Heart Failure

• Acute decompensated heart failure or pulmonary edema: Start with 20-40 mg IV bolus given over 1-2 minutes 1, 2
• Chronic heart failure with mild edema: Begin with 20-40 mg orally once daily 2, 3
• For patients already taking >40 mg daily at home who present acutely, start with at least their home dose IV (typically 80 mg) 1
• Total dose should remain <100 mg in the first 6 hours and <240 mg in the first 24 hours for acute presentations 1, 2

Cirrhosis with Ascites

• Always start with combination therapy: Furosemide 40 mg + spironolactone 100 mg as a single morning dose 1, 2
• Maintain the 100:40 spironolactone-to-furosemide ratio when escalating 1, 2
• Increase both drugs simultaneously every 3-5 days if weight loss is inadequate 1, 2
• Maximum furosemide dose is 160 mg/day; exceeding this indicates diuretic resistance requiring alternative strategies like large volume paracentesis 1
• Prefer oral over IV route to avoid acute GFR reduction 1

Nephrotic Syndrome

• Pediatric patients: Start with 0.5-2 mg/kg per dose IV or orally, up to six times daily (maximum 10 mg/kg/day) 1
• Administer IV furosemide 0.5-2 mg/kg at the end of albumin infusions when marked hypovolemia or hyponatremia are absent 1
• High doses (>6 mg/kg/day) should not be given for longer than 1 week 1

Pediatric Dosing (General)

• Initial dose: 2 mg/kg body weight as a single dose 3
• May increase by 1-2 mg/kg no sooner than 6-8 hours after previous dose 3
• Maximum: 6 mg/kg body weight per day 1, 3

Dose Escalation Strategy

When Initial Dose is Inadequate

• If no response after 6-8 hours: Increase by 20-40 mg increments 1, 3
• For severe edematous states, doses may be carefully titrated up to 600 mg/day 3
• Beyond 80-160 mg/day: Consider adding a second diuretic (thiazide or aldosterone antagonist) rather than further escalating furosemide alone 1

Continuous Infusion Alternative

• After initial bolus, consider continuous infusion at 5-10 mg/hour (maximum rate 4 mg/min) 1
• This approach may be more effective than repeated boluses in diuretic-resistant patients 4

Critical Pre-Administration Requirements

Do not administer furosemide if any of the following are present: 1, 2

• Systolic blood pressure <90-100 mmHg (without circulatory support)
• Marked hypovolemia
• Severe hyponatremia (serum sodium <120-125 mmol/L)
• Anuria
• Severe hypokalemia (<3 mmol/L)

Administration Considerations

Route Selection

• IV preferred for: Acute situations requiring rapid diuresis, gut edema reducing oral absorption 1
• Oral preferred for: Cirrhotic patients (better bioavailability, avoids acute GFR reduction), chronic maintenance therapy 1
• Infusion rate: Doses ≥250 mg must be given over 4 hours to prevent ototoxicity 1

Timing

• Single morning dose maximizes compliance and reduces nighttime urination 1, 2
• Peak effect occurs 1-1.5 hours after oral administration, faster with IV 1
• If twice-daily dosing needed, give second dose at 2 PM (not evening) 1

Monitoring Requirements

Initial Phase (First Week)

• Urine output: Place bladder catheter in acute settings for hourly monitoring 1
• Daily weights: Target 0.5 kg/day loss without peripheral edema, 1.0 kg/day with peripheral edema 1
• Electrolytes: Check sodium, potassium, creatinine every 3-7 days 1
• Blood pressure: Every 15-30 minutes in first 2 hours after IV administration 1

Ongoing Monitoring

• Weekly electrolytes after stabilization 1
• Watch for signs of hypovolemia: decreased skin turgor, hypotension, tachycardia 1

Common Pitfalls to Avoid

• Never use furosemide to treat or prevent acute kidney injury—only for managing volume overload that complicates AKI 1
• Do not give to hypotensive patients expecting hemodynamic improvement; it worsens tissue perfusion 1
• In acute pulmonary edema, do not use as monotherapy—combine with IV nitroglycerin for superior outcomes 1
• Avoid evening doses—they cause nocturia without improving outcomes 1
• Do not exceed 160 mg/day in cirrhosis without considering alternative strategies 1

Special Populations

Geriatric Patients

• Start at the low end of the dosing range (20 mg) 3
• Titrate cautiously with careful monitoring 3

Renal Impairment

• Higher doses may be required due to reduced drug delivery to the loop of Henle 1
• Consider adding a second diuretic rather than escalating beyond 160 mg/day 1

Diuretic Resistance

• Add thiazide (hydrochlorothiazide 25 mg) or aldosterone antagonist (spironolactone 25-50 mg) 1
• Consider continuous infusion instead of bolus dosing 1, 4
• In cirrhosis specifically, proceed to large volume paracentesis rather than exceeding 160 mg/day 1